Isogonal moulding surfaces: A family of shapes for high node congruence in free-form structures

• Connections are key to structural cost in free-form architecture.
• A formal framework for construction-aware design is proposed.
• The structural layouts derived from this framework have high node repetition.
• The framework can be applied to stadia, domes and building facades.
• Numerical implementation allows real-time exploration of the framework.

The design of free-form structures is governed by structural and geometric considerations, the latter ones being closely linked to the costs of fabrication. If some construction constraints have been studied extensively, the question of the repeatability of nodes in free-form structures has rarely been addressed yet. In this paper, a family of surfaces that can be optimized regarding typical geometrical constraints and that exhibit high node congruence is proposed. They correspond to particular meshes of moulding surfaces and are called isogonal moulding surfaces by the authors. The geometrical properties of these surfaces are discussed. In particular, it is shown how to derive edge offset mesh from them. It is also demonstrated that they represent all the possible meshes parallel to surfaces of revolution. Finally, the reader is introduced to some computational strategies linked to isogonal moulding surfaces.